If you regularly turn to a search engine to find out whether, say, you should put ice on a twisted ankle, you're far from alone. Sixty-one per cent of American adults seek out health advice online, according to a survey published last month by the Pew Internet and American Life Project.

Around a third of those surveyed admitted they changed their thinking about how they should treat a condition based on what they found online. Yet a growing body of evidence suggests that much online health information is unreliable.

Several studies to be published in medical journals this year highlight the issue. Pia López-Jornet and Fabio Camacho-Alonso of the University of Murcia, Spain, found that information on oral cancers on the top websites gathered by Google and Yahoo searches was "poor" (Oral Oncology, DOI: 10.1016/j.oraloncology.2009.03.017). Among other things, the websites failed to attribute authorship, cite sources and report conflicts of interest. And a study by a team at the Charité University Medical Centre in Berlin, Germany, of googled advice on how to deal with heartburn found that "the evidence for most of the recommendations is weak to nonexistent" (European Journal of Integrative Medicine.